The present invention relates to a method of manufacturing an ink-jet printhead.
The method according to the invention can be applied for production of both thermal ink-jet printheads and piezoelectric ink-jet printheads.
Known ink-jet printheads comprise a silicon substrate, which includes the active ejecting elements, i.e. the thermal ejectors or the piezoelectric ejectors.
Known printheads also include a hydraulic structure layer, that define hydraulic circuits through which ink flows, and an orifice plate having a plurality of nozzles for ejection of said ink onto the medium to be printed.
The orifice plate can be made, for example, by electro-plating of a layer of nickel, that may be covered by a gold or palladium additional layer.
It is to be noted that the known processes for manufacturing printheads include a step of thermo-compression, through which the different layers are fixed together.
In this respect, orifice plates made of nickel present severe drawbacks since nickel and silicon have significantly different behaviours when heated at 150° C.-200° C. (i.e. at temperatures typical of thermo-compression processes).
Therefore, a precise mutual positioning of the silicon chips and respective nozzles can not be obtained. In particular, this problem becomes very critical with the increasing length of the chip and nozzle plate.
Furthermore, residual forces due to the rigid connection between elements having different thermal behaviours can even cause breaking of the silicon chips and/or detachment of the different parts of the printhead.
This effect is particularly critical in industrial applications, wherein the volume of the ink droplets is larger than in standard applications. This implies that the orifice plate can be very thick and produce higher stress due to thermal expansion.
Another drawback of the nickel orifice plates consists in that such orifice plates can not be used in certain industrial applications, wherein industrial abrasive inks cause progressive damaging of the nickel and/or possible gold/palladium protective layer.
It is to be noted that also chemical corrosion problems may arise when certain industrial inks are used.
An additional drawback related to nickel orifice plates consists in the inherent low precision of the electro-formation process, that necessarily causes misalignments between the nozzles and the corresponding chips and hydraulic structures.